Graphene is a new carbonaceous material with ideal two-dimensional crystalline structure, at present it has the most outstanding conductivity performance, it has a saturation drift velocity of 5.5×107 cm/s, and a carrier mobility of greater than 200,000 cm2/Vs, and it is suitable for making ultra-high frequency device. After recent several years of research and development, the current cut-off frequency ƒT of graphene transistor has reached 427 GHz, but it is still far from the ideal value, and the large resistance of access region is one of the main factors affecting the performance of graphene devices. As the size of a device decreases, the resistance of access region is substantially equivalent to the channel resistance of the device, which significantly affects the device performance. Therefore, the device performance can be improved by reducing the resistance of access region, i.e., reducing the spacings of the ungated region between the gate and the source contacts, between the gate and the drain contacts as much as possible. Meanwhile, because the graphene has special two-dimensional crystal structure, some water molecules and residual photoresist are easy to be absorbed onto the graphene surface in the device processing, resulting in doping and contamination to the obtained graphene material, which is another important factor affecting the performance of graphene device.